Digging into Pandora’s Music Genome with musicologist Nolan Gasser

Pandora online is best known for its enormous storehouse of popular music, but …

"It's hard to believe that it was ten years ago," Pandora radio's Chief Musicologist Nolan Gasser confided to me in a recent interview. "I was completing my doctorate in musicology at Stanford, and was at a crossroads—between going into academia, and exploring my options as an independent musician.”

It was in that context that Gasser, now an accomplished composer, pianist, and musicologist, heard that Pandora online radio founder Tim Westergren was looking for graduate students to help analyze music for a start-up music technology company.

"This was early 2000, and the words 'music' and 'technology' were just beginning to be used in the same sentence," Gasser noted.

"I answered the e-mail, and soon met with Tim—who recognized that I was not only capable of becoming a music analyst, but was able to help him realize his vision: to marry the realms of music analysis and database technology, and to create what became the Music Genome Project. It was Tim's brainchild to put these two worlds together, and happily I was the right guy at the right time and place, with the background to be able to actually design the thing."

Today, Gasser is recognized as the architect of the Music Genome—the extensive database of musical attributes that lets Pandora intuit from the songs and compositions you pick what other kinds of music would please your ears.

I listen to Pandora all the time, and most of the channels I've created stream classical fare. Pandora literally saved classical music broadcasting for me. Like so many lovers of Bach, Bartok, and Stravinsky, I've experienced the last two decades as a huge disappointment. Scores of commercial classical stations disappeared after the huge license sell-off that followed the Telecommunications Act of 1996, which made it much easier to purchase radio outlets.

Even many public radio stations have let the classical tradition go. Recent figures compiled by National Public Radio indicate that one in five noncommercial stations abandoned the classical format between 2001 and 2010. Quite of few of the surviving broadcasters stay afloat by sticking to lighter fare, avoiding anything too long or too adventurous (although one of my favorite public stations, KUSC-FM, bucks that trend).

Pandora, on the other hand, offers an endless stream of unexpected delights—symphonies, sonatas, arias, and concertos by composers with whom I'm only vaguely familiar. But I've always wanted to know exactly how the service did this, and also how the classical component of Pandora differs from its more well known storehouse of popular music.

And so I contacted Pandora, and Nolan Gasser and I had this conversation.

Nolan Gasser, Chief Musicologist for Pandora

Q. Nolan, what have you been doing at Pandora over the last decade?

Well, I can only tell you so much, otherwise we might have to kill you (just kidding). Being a musicologist, as well as a pianist and a composer, I'm fortunate to have had a pretty eclectic background: I'm probably most at heart a classical musician, but I've been playing and writing rock and roll and jazz since I was very young; I've always been an eclectic musical animal.

The basic idea with Pandora was to see if we could approach music from almost a scientific perspective; that's why it's called the Music Genome Project, named not accidentally after the Human Genome Project.

I've always taken that metaphor very seriously: biologists have come to understand the human species by identifying all the individual genes in our genome; it's then how each individual gene is manifest or expressed that makes us who we are as individuals—as well as defines how we're related to others: most closely to those in our family, but also indirectly to people who share our same physical attributes or capabilities in sports, and so forth.

That orientation was paramount to my thinking in designing the Music Genome Project. The idea was to tackle in turn each distinct "species" of music—and we naturally started with the most vibrant one in the music industry: pop and rock music. So my tack was to conceive of pop/rock as an individual musical species, and then to figure out what individual genes make up its genome.

From a musicological standpoint, we can break down the musical identity of a pop/rock song into the fundamental parameters of music analysis: melody, harmony, rhythm, form, instrumentation, sonority, lyrics, and several others. We can then break down each of these large-scale parameters into detailed and nuanced individual traits—or genes—that are manifest in some way or another in every pop/rock song.

Q. Let's begin with popular music. How does Pandora handle that?

With pop/rock music, you are really dealing with the recording as a fixed entity. When you listen to a recording of a rock song, such as "Hey Jude" by the Beatles, you're experiencing—on some level—each of the parameters I mentioned earlier, as being manifest in a fixed and very specific way.

So, in the parameter of melody, for example, both the verse and the bridge (there really isn't a chorus in "Hey Jude") are what we'd call "through-composed," as opposed to being constructed with lots of short repeating figures (like, say, in "A Hard Day's Night"). The melody of "Hey Jude" also has a wide range (over an octave for both sections), compared to a more narrow-ranged song, like "Drive My Car." And there are lots of other ways in which we can define how melody functions in this song: What is the rhythmic character of the melody? What is the relationship between the melody and the lyrics? Etc., etc.

We then take a similar approach to evaluating the song's other parameters: its use of harmony, form, the sound of Paul McCartney's voice, the instrumentation (the use of piano, for example), and so forth.

Form, in fact, is very interesting here: I mentioned how "Hey Jude" doesn't really have a chorus the way that most pop/rock songs do—and in this way it breaks from what we'd expect of a "standard" song of this species. Another big distinction is that "Hey Jude" has a very unique ending or coda. A lot of pop/rock songs have a tag or coda [literally "tail"], but very few have a coda in the way that "Hey Jude" does—where the same 4 bar phrase (the "na-na-na" line) is repeated for some 4 minutes!

Scriabin Piano Sonata No. 3; first movement

So, these are just a few of the ways in which "Hey Jude" expresses the genes found in the pop/rock genome in its own unique way, and which make it similar to some songs and different from others in the same genome—which in turn can help people find or avoid songs that share those same traits.

Matthew Lasar / Matt writes for Ars Technica about media/technology history, intellectual property, the FCC, or the Internet in general. He teaches United States history and politics at the University of California at Santa Cruz.